COPD has become a major cause of morbidity and mortality in the United States over the last three decades. COPD is characterized by the presence of airflow obstruction due to chronic bronchitis or emphysema. The airflow obstruction in COPD is due largely to structural abnormalities in the smaller airways. Important causes are inflammation, fibrosis, goblet cell metaplasia, and smooth muscle hypertrophy in terminal bronchioles.
The incidence, prevalence, and health-related costs of COPD are on the rise. Mortality due to COPD is also on the rise. In 1991, COPD was the fourth leading cause of death in the United States and had increased 33% since 1979. COPD is a progressive disease and currently has no cure. Current treatments for COPD include the prevention of further respiratory damage, pharmacotherapy, and surgery. Each is discussed below.
The prevention of further respiratory damage entails the adoption of a healthy lifestyle. Smoking cessation is believed to be the single most important therapeutic intervention. However, regular exercise and weight control are also important. Patients whose symptoms restrict their daily activities or who otherwise have an impaired quality of life may require a pulmonary rehabilitation program including ventilatory muscle training and breathing retraining. Long-term oxygen therapy may also become necessary.
Initially, hundreds of patients underwent a procedure called lung volume reduction surgery (LVRS), in which the most affected parts of the lungs are surgically removed. This procedure restores the tethering force that tends to keep intrathoracic airways open, which was lost in emphysema. However, the procedure has fallen out of favor due to the fact that Medicare stopped remitting for LVRS. Unfortunately, data is relatively scarce and many factors conspire to make what data exists difficult to interpret. The procedure is currently under review in a controlled clinical trial. However, what data does exist tends to indicate that patients benefited from the procedure in terms of an increase in forced expiratory volume, a decrease in total lung capacity, and a significant improvement in lung function, dyspnea, and quality of life.
Improvements in pulmonary function after LVRS have been attributed to at least four possible mechanisms. These include enhanced elastic recoil, correction of ventilation/perfusion mismatch, improved efficiency of respiratory musculature, and improved right ventricular filling.
Lung resection has a drawback in that it is difficult to seal against leaks once tissue has been resected. Lung tissue includes thin, fragile, and slippery blood vessels and air passageways that are difficult to suture against leaks. After the diseased tissue is removed, the remaining or resectioned lung portion is often restructured with suture staples. In about thirty percent of these cases, sutured lung tissue leaks air because the vessels were not adequately sealed. In other cases, sutured lung tissue leaks blood from the resection site for the same reason. Treatment for such leaks depends upon their severity, and often requires further open-chest surgery.
Previous efforts have been disclosed to treat COPD and other related pulmonary diseases by applying a constriction device to selected target tissue for purposes of resection in a manner that substantially minimizes the risk of leak, but also reduces the trauma resected with traditional lung volume reduction surgery. Such efforts are described in U.S. Pat. Nos. 6,328,689, 6,485,407, 6,491,706, 6,632,239, 6,589,161, 6,790,172 and 6,843,767, and U.S. application Ser. No. 09/901,764, all of which are incorporated herein by reference. In that regard, a constriction device having one of varying configurations can be selectively applied to a portion of target lung tissue by a delivery system, described somewhat schematically in one or more of the above patents. Such a delivery system has been disclosed in the prior art with more specific features that include an introducer and a loader in which the desired constriction is applied to a delivery system via a loader and then introduced onto the lung for release and ultimate resection. These prior art systems, while very beneficial in the delivery of such constriction devices, were more complicated to operate and required a multiple step operation that may be perceived adversely by the clinician. Thus, improvements have been made to a device capable of delivering a constriction device to a target lung portion, as described herein.